Bokeh refers to the aesthetic quality of out-of-focus blur. This calculator computes the circle of confusion size and relative bokeh strength to help predict background separation.
Bokeh quality depends on aperture blade count and shape (circular blades produce rounder highlights), lens optical design, and the size of the out-of-focus highlight relative to the CoC. Larger apertures, longer focal lengths, closer subject distances, and more distant backgrounds all increase background blur. Lens design — particularly the number and shape of aperture blades — affects whether bokeh circles appear smooth or polygonal.